Born in York, Moran's first produced work came as the result of a competition run by the Sci Fi Channel. The competition asked for writers to submit short science-fiction themed film scripts. Moran won, and his entry Cheap Rate Gravity was produced and shown both on the sci-fi channel and in front of full length movies, including Final Destination 2.

Moran scripted the 2005 film Severance, which concerns office workers on a team building trip being stalked by a masked killer.

Moran's television writing debut was writing episodes for Doctor Who, and its spin-off, Torchwood. He lobbied his agent for many years to get him a job on either show. Moran's first Torchwood episode, "Sleeper", was the second to be transmitted in the second series, and concerns a burglary that goes wrong, revealing a plot that leaves the whole planet in danger. There are many allusions to terrorism during the episode, and filming on several controlled explosions in Cardiff was almost disrupted by a real terrorist attack in Glasgow. "Sleeper" was broadcast by BBC Two on 23 January 2008. Moran also co-wrote the Torchwood episode, "Day Three" of "Children of Earth" with Russell T Davies which was first broadcast on 8 July 2009.[9]

Moran's Doctor Who episode, "The Fires of Pompeii"  set during the eruption of Mount Vesuvius  was broadcast on 12 April 2008 as part of the revived programme's 4th series.